The present invention relates to a low-pressure actuator for use in a dry, pressurized-air, fire control and suppression sprinkler system, that typically uses water as the extinguant or extinguishing liquid. The low-pressure actuator of the present invention is applicable for use in a dry type fire control and suppression sprinkler system, in which the piping between the pressurized extinguishing water source and individual sprinkler heads is normally void of water. The low-pressure actuator of the present invention is particularly applicable to low-pressure dry type sprinkler systems, wherein the system gas (typically air) pressure is not greater than about 20 psi.
Fire control and suppression sprinkler systems generally include a plurality of individual sprinkler heads, which are usually ceiling mounted about the area to be protected. The sprinkler heads are normally maintained in a closed condition and include a thermally responsive sensing member to determine when a fire condition has occurred. Upon actuation of the thermally responsive member, the sprinkler head is opened, permitting pressurized water at each of the individual sprinkler heads to freely flow therethrough for extinguishing the fire. The individual sprinkler heads are spaced apart from each other, by distances determined by the type of protection they are intended to provide (e.g. light or ordinary hazard conditions) and the ratings of the individual sprinklers, as determined by industry accepted rating agencies such as Underwriters Laboratories, Inc., Factory Mutual Research Corp. and/or the National Fire Protection Association. It should be well appreciated that once the sprinkler heads have been thermally activated there should be minimal delay for the water flow through the sprinkler head at its maximum intended volume.
In order to minimize the delay between thermal actuation and proper dispensing of water by the sprinkler head, the piping that connects the sprinkler heads to the water source is, in many instances at all times filled with water. This is known as a wet system, with the water being immediately available at the sprinkler head upon its thermal actuation. However, there are many situations in which the sprinkler system is installed in an unheated area, such as warehouses. In those situations, if a wet system is used, and in particular since the water is not flowing within the piping system over long periods of time, there is a danger of the water within the pipes freezing. This will not only deleteriously affect the operation of the sprinkler system, should the sprinkler heads be thermally actuated while there may be ice blockage within the pipes, but such freezing, if extensive, can result in the bursting of the pipes, thereby destroying the sprinkler system. Accordingly, in those situations it is the conventional practice to have the piping devoid of any water during its non-activated condition. This is known as a dry fire protection system.
All fire protection sprinkler systems generally include a check valve for isolating the sprinkler system piping from the pressurized water source during the non-activated condition. The check valve, which is physically interposed between the system piping and the pressurized water source, includes a clapper, which when it is in its closed operative condition prevents the flow of pressurized water into the sprinkler system piping. The sprinkler piping in the dry fire protection system includes air or some other inert gas (e.g. nitrogen) under pressure. The pressurized air, which is present within the sprinkler system piping, is also presented to the check valve. Should one or more of the sprinkler heads be thermally activated to its open condition, the pressure of the air within the sprinkler system piping and check valve will then drop. The check valve must be appropriately responsive to this drop in pressure, normally in opposition to the system water pressure also present in the check valve, to move the clapper to its open condition. When this occurs, it is desirable to have a rapid expulsion of the pressurized air within the check valve and the sprinkler system piping, to permit the rapid flow of the pressurized water through the open check valve, into the sprinkler system piping, and through the individual sprinkler heads to rapidly extinguish the fire.
The check valves intended for dry type fire control sprinkler systems have typically controlled the clapper movement by the water and the air pressure applied to its opposite sides. Such fire check valves include an air seal, which opposes the pressurized water seal. To appropriately apply the system air pressure over the surface of the clapper air seal, a priming water level is oftentimes maintained within the check valve. During normal conditions, when no sprinkler heads have been activated, the two seals will be at equilibrium, thereby maintaining the clapper in its closed condition.
In order to increase the speed of check valve operation upon a drop off of the system air pressure, occasioned by the activation of one or more sprinkler heads, the system air pressure is normally applied to the clapper air seal over a substantially greater area than the water pressure is applied to the clapper water seal. This is known as a high-differential-type check valve. A problem of such valves is that should there be a reduction in the system water pressure after the clapper has opened, there is a tendency for the clapper to reclose, particularly since the pressure against the opposite (air) side of the clapper has thereby been increased due to the column of water that has flowed therethrough. Since the pressure applied against the air seal of the clapper will now be increased by the column of water extending upwards from the re-closed check valve, a greater water pressure would now be required to move the clapper to its open condition. Such disadvantageous re-closure is referred to as a water columning effect. This could result in failure of the check valve to subsequently open should one or more of the sprinkler heads be thermally activated.
In order to avoid the re-closure of the clapper, dry system check valves have generally been provided with a mechanical latch to maintain the clapper in its open condition once it has been activated. The inclusion of such a mechanical latch, while serving to prevent re-closure, however, disadvantageously requires the entire sprinkler system to be shut down and the interior of the high differential type actuator accessed to release the latch and re-close the clapper after the fire has been extinguished. Thus, check valves have typically required the main supply of water to be shut off, the water drained from the system, and then the high differential check valve opened to manually unlatch and reset the clapper. Recognizing the disadvantage of having to manually access the interior of the check valve, a mechanism is shown in U.S. Pat. Nos. 5,295,503 and 5,439,028, which include a reset linkage mechanism that is attached to the check valve, and is actuated by the rotation of an externally accessible handle. As can be well appreciated such a mechanism adds to the size, cost and complexity of the check valve.
Another way by which the response of a system check valve can be made faster upon activation is to incorporate a low-pressure actuator into the system. Actuator-accelerators for fire control and suppression sprinkler systems, including the low-pressure actuator of the present invention, are pilot valves that are designed to actuate the check valve. Actuators for dry fire protection systems, including the low pressure actuator of the present invention, detect a decline in system pressure due to a triggering event, such as the opening of a sprinkler head, and cause the valve to operate in order that water or another extinguishing liquid utilized in the system can flow into and fill the system as rapidly as possible so as to minimize the time it takes for the water to reach and be distributed to the multiple individual sprinkler heads of the system and be applied to extinguish a fire.
Traditionally, dry pipe valves used in sprinkler systems employ pressurized air in order to keep water from entering the sprinkler system. Although this pressurized air is given a mechanical advantage over the water pressure, typically of from about 5-8:1, typical air pressures in dry sprinkler systems are from 30 psi to 50 psi. Displacement of this volume of air from the piping of the sprinkler system will delay the operation of the sprinkler control valve, as well as slow the rate of water entry into the sprinkler system once the control valve is actuated.
For example, given a supply water pressure of 80 psi and a sprinkler control with an 8 to 1 water to air ratio, and given that a sprinkler head activates when the system air pressure is at 30 psi, the air pressure must decay from 30 to 10 psi before the valve will activate. Also, once the valve activates, the remaining 10 psi of air pressure must still be exhausted before the water can completely fill the sprinkler system.
In the case of using an actuator-accelerator, given a supply water pressure of 80 psi, if a head activates when the system air pressure is at 30 psi, the accelerator will activate on a rapid pressure drop of less than 5 psi. Although this will greatly reduce the time required for the valve to operate, the remaining 25 psi air pressure must still be exhausted before the sprinkler system becomes filled with water.
It is, therefore, advantageous to have as little air as possible in the system, in order to obtain the most rapid delivery of water to the sprinkler heads of a dry sprinkler system.
In the fire protection industry there also exists a specialized class of sprinkler control valves, which provides added security against the accidental discharge of water into or from the sprinkler system. These systems are known as pneumatic/electric double interlock systems. Such systems are frequently used in refrigerated spaces. These systems contain air pressure in the sprinkler system in order to prevent either accidental discharge of water or the freezing of any water in the sprinkler-piping network.
In order to provide this added security, these systems require that two separate events must occur in order for the sprinkler control valve to activate and allow water into the sprinkler system. In the preferred embodiment these two events consist of a sprinkler head activating, thus discharging air pressure from the sprinkler system, and an electrical detection. The electrical detection can be from any number of devices, such as, but not limited to, smoke, heat and rate of temperature rise detectors. There is also a need in the art for a low-pressure actuator for use in conjunction with such a system.
As used herein, the terms gas and air are used substantially interchangeably to refer to the non-liquid fluid utilized in the apparatus and system, where air is the gas most typically used; and the terms liquid and water are used substantially interchangeably to refer to the liquid fluid utilized in the apparatus and system, where water is the liquid most typically used.
The low pressure actuator of the present invention is designed to rapidly reduce the water pressure that is applied to the check valve plunger upon the occurrence of an air pressure drop occasioned by the thermally responsive opening of one or more of the sprinkler heads.
More specifically, the present invention provides a low-pressure actuator for a check valve, having particular utilization in conjunction with a dry fire control sprinkler system in which the system piping is normally devoid of water, and includes pressurized air (or other inert gas).
It is desirable to operate such systems at as low a system gas pressure as possible to minimize the time required for gas pressure to fall when the system is actuated, and thereby minimize the time to clear the system piping and lines of air so that an extinguishing liquid can be delivered to the sprinkler heads as rapidly as possible. The low-pressure actuator of the present invention is designed to operate in systems where the system gas or air pressure is not greater than about 20 psi, and is preferably about 10 psi, or even lower.
Typically water is used as the fire extinguishing fluid, although other liquids can be used, including fire suppressing and retarding chemicals, either alone, or added to water to form a solution.
The low-pressure actuator comprises a housing, which has an outlet at one end, which is connected to the pressurized air of the fire control sprinkler system. The opposite end of the low-pressure actuator has an inlet, which is connected, to the source of pressurized water. A plurality of chambers is provided between the water inlet and air outlet, with a system of air and water pressure-sensitive diaphragms. The low pressure actuator will have a closed operative condition during which time it isolates the check valve, and hence the sprinkler system piping, from the pressurized water source, and an open operative condition in which it allows the pressurized water to freely flow through itself and the check valve and into the sprinkler system piping. A seal is provided which includes cooperating flexible pressure seals, of minimal differential area. The pressurized air is applied against one of the seals, and pressurized water against the other seal. The diaphragm system includes an upper, air pressure-sensitive diaphragm and a lower, water pressure-sensitive diaphragm. The low-pressure actuator includes a tripping device for establishing air pressure in the unit.
The air pressure seal has a substantially greater area than the water pressure seal. The ratio of the water pressure seal area to the air pressure seal area is greater than about 20:1 and may be as high as about 600:1, or higher. When the pressure being applied over the areas of the air and water pressure seals are in equilibrium, these seals will be in a first operative condition. When a predetermined pressure has been reached in the first chamber, the tripping device operates, causing air in the first chamber to be exhausted to atmosphere. The air pressure seal will then no longer be in equilibrium with the water pressure seal. That seal will then be flexed towards the first chamber and move to a second operative condition. When this occurs, the seal between the inlet and outlet openings of the water chamber will open, no longer blocking the communication between the inlet and outlet openings. This will then allow the system water pressure from the line in common with the check valve plunger to drain. The check valve is then rapidly operated to its open condition.
The tripping device is used to pressurize the low-pressure actuator. The tripping device has a spring which is biased to maintain the tripping device in a closed position when the low pressure actuator and the tripping device itself are pressurized at the system pressure. The tripping device has an air pressure seal to spring-constant force ratio. When the gas pressure in the gas compartment falls due to a fall in system gas pressure, caused by an opening in the system, such as caused by an actuated sprinkler head, the spring force will exceed the counter-balancing force due to gas pressure in the gas compartment, at some level, causing the spring to open the outlet of the tripping device and causing the remaining air therein to flow out, further lowering the gas pressure in the actuator, thereby causing it to become actuated and water to flow through the actuator to the check valve, which is opened, thereby also releasing water to the sprinkler heads. Thus, the low-pressure actuator can be set to respond when the system gas pressure falls to a predetermined value, by providing a spring for the tripping device having a particular spring constant and an air pressure to spring force ratio that will cause the tripping device to open when the predetermined lower gas pressure value is reached. By selecting a spring with a lower spring constant, the tripping device will not open until a lower system gas pressure is reached; and by selecting a spring with a higher spring constant, the tripping device will be caused to already open when there has been only a relatively small drop in system gas pressure.
Modified embodiments of the low pressure actuator according to the present invention include those which can provide even more rapid operation in response to a drop in the system air pressure, occasioned by the opening of one or more sprinkler heads. A particularly preferred embodiment of low pressure actuator according to the present invention incorporates a three-chamber housing, has a dual diaphragm based system, where a first diaphragm provides a gas-liquid seal, and a second diaphragm provides a water-dry seal when the low pressure actuator is in the closed condition and is open to liquid contact on both sides when the low pressure actuator is in an actuated, open condition. This embodiment typically operates at a system gas pressure of about 10 psi, but is capable of operating at even lower pressures.
The system pressurizing gas is applied to the first diaphragm in the first chamber. Pressurized system extinguishing liquid flows into the third chamber.
A restrictor is provided between the liquid side of the upper diaphragm in the gas compartment and the liquid compartment. When a drop in the system air pressure occurs, the gas compartment will have a drop off of its internal air pressure, corresponding to the drop in system pressure. Actuation of the tripping device causes the upper diaphragm to be displaced by the greater liquid pressure on the wet side of the upper diaphragm, causing water to flow through a by-pass orifice which was previously sealed and is opened by the moved diaphragm, thereby causing liquid to flow through to the outlet. In turn, this causes the second diaphragm to be displaced and a greater liquid flow to the liquid outlet occurs.
It is, therefore, a primary object of the present invention to provide an improved low-pressure actuator, having particularly utilization in conjunction with dry fire control and suppression sprinkler systems.
Another object of the present invention is to provide a low-pressure actuator for use in dry fire control and suppression systems, wherein the low-pressure actuator has a single set point regardless of the system liquid pressure.
Still another object of the present invention is to provide a low pressure actuator for use in dry fire control and suppression systems, wherein the time for system gas pressure to vent and extinguishing liquid to flow to sprinkler heads of the system is greatly reduced.
An additional object of the present invention is to provide a low-pressure actuator for use in dry fire control and suppression systems, wherein the low-pressure actuator is responsive to a decline in system gas pressure.
Yet another additional object of the present invention is to provide a low-pressure actuator for use in dry fire control and suppression systems utilizing a low-differential check valve.
A still further additional object of the present invention is to provide a low pressure actuator for use in dry fire control and suppression systems, wherein a low system gas pressure is advantageously utilized to maintain the low pressure actuator in a closed position in opposition to a substantially higher extinguishing liquid pressure.
Yet another additional object of the present invention is to provide a low-pressure actuator, which provides a fast response to the check valve and prevents air and water buildup in the low-pressure actuator.
Still an additional object of the present invention is to provide a low-pressure actuator that operates at low system gas pressure so as to enable the use of a smaller gas compressor as part of the system.
One further object of the present invention is to provide a low-pressure actuator with a pneumatic/electrical double interlock safety feature, for use in certain applications, such as for use in a dry sprinkler system for a refrigerated space.
These as well as other objects of the present invention will become apparent upon a consideration of the following detailed description and drawings.